1. Field of the Invention
This invention relates to a method of mounting a rubber plug to a wire used for a waterproof connector in which the fluctuation in the position of the rubber plug about the wire is reduced.
2. Description of the Prior Art
In a waterproof connector used for connecting wire harnesses, a rubber plug 2 is inserted into an end of a wire 1 as illustrated in FIGS. 7A to 8B, and then a terminal 23 is calked so as to be fixed to the wire together with the rubber plug.
The rubber plug 2 consists of a thin portion 2a with a small diameter and a thick portion 2b with a large diameter, as illustrated in FIGS. 8A and 8B. A wire insertion hole 2c is formed in the rubber plug 2, and a tapered wire insertion guide 2d is formed in the wire insertion hole 2c on the side that the wire 1 is inserted. Further, projections 2e are formed on an outer periphery of the thick portion 2b. Reference symbol L1 shows the length of the thin portion 2a. L2 shows the length of the thick portion 2b.
After the wire 1 is positioned so as to project, from an end of the thin portion 2a of the rubber plug 2 by a predetermined length D as illustrated in FIG. 7A, an insulating coating 1b is removed by a stripping device not shown. Conductor crimping pieces 23b of a wire connecting portion 23B of the terminal 23 in FIG. 7B are used to crimp an exposed core wire 1a, and insulating calking pieces 23c crimp the thin portion 2a with a small diameter. Reference symbol 23A shows an electrical contact portion for a mated terminal and Reference Numeral 23a shows a resilient contact piece.
FIGS. 9 and 10 show a rubber plug mounting method with a conventional rubber plug mounting apparatus, as disclosed in Japanese patent publication (examined) No. Showa 64-9131. Reference numeral 4 shows a jig and a rubber plug accommodating portion 5 with a tiered portion concavely formed therein. The rubber plug accommodating portion 5 consists of a large hole 5a with a diameter substantially the same as that of the thick portion 2b of the rubber plug 2, and a small hole 5b with a diameter sufficiently larger than that of thin portion 2a of the rubber plug 2.
The rubber plug 2 is accommodated in the accommodating portion 5 in advance, and the wire 1 is aligned with the wire insertion hole 2c by a pair of guides 6 and 6' which are vertically arranged. Then, the mounting jig 4 proceeds in the direction indicated by an arrow P toward the wire 1, and the guides 6 and 6' are simultaneously moved in the same direction at the same velocity to insert the rubber plug 2 to the wire 1 by a predetermined length as illustrated in FIG. 9. The length that the rubber plug 2 is inserted is the sum of an overall length of the rubber plug 2 and a prescribed projection length D. Finally, the jig 4 is moved in the direction indicated by an arrow P' to release the rubber plug, which permits a projecting length of the wire 1 from the thin portion 2a to be adjusted to the predetermined length D as illustrated in FIG. 10. However, with the method described above, a return .DELTA.L of the rubber plug 2 is generated as a matter of fact, which provides a gap between the guides 6 and 6'. As a result, a projecting length D' does not coincide the setting value D, resulting in fluctuation in the position of where the rubber plug 2 is situated about the wire 1.
The reason for the fluctuation is because the resilient thin portion 2a with a small diameter elongates by .DELTA.L1 from an original length L1 due to a frictional resistance between the wire insertion hole 2ac of the rubber plug 2 and the wire 1, as illustrated in FIG. 11A. The release from the jig 4 causes the thick portion 2b with large diameter of the rubber plug 2 to move on the side of the thin portion 2a with small diameter 2a by the resilience of the overall rubber plug 2. However, the return length is fluctuated due to dimensional tolerance and uneven resilience of the rubber plug 2. Therefore, even if the insertion length of the rubber plug 2 to the wire 1 is constantly maintained, the fluctuation in the position of the rubber plug 2 could not be prevented effectively.